Carburetor choke control



Nov..11, 1941. 5 L, R D-+- 2,262,408

CARBURE' IOR CHOKE CONTROL Filed Feb. 27, 1941 INVENTOR.

LELAND B. READ .5 t UNITED: "STAT Patente'ci' Nov'. 1 1;

Es PATENT ori ice 6 Claims. This invention relates to carburetors forinternal combustion engines and more particularly to automatic chokecontrol devices therefor.

Many of the current automaticv choke constructions involve theuse of aspirally wound bi-metallic element which is either directly attached tothe choke valve shaft ordisposed immediately adjacent thereto andsubjectedto a controlled amount of heat conducted thereto from some partof the engine which becomes 'more quicklyheated after starting. Themeans employed for controlled heating usually comprises providing ahousingfor the coil, a stove I or heating jacket attached to the exhaustmanifold and a conduit for conducting the heated air from the stoveto'the coil housing. 'The flow of warm airfrom the'stove to the coilhousing being induced and. controlled by a calibrated and sometimesvariable passageway connecting -the coil housing with a zone of highsuction in the carburetor mixture conduit.

In downdraft carburetor constructions in which -the air inlet and chokevalve areat'the'upper end of the carburetor, it will be seen that whenthe choke control coilis arranged in the above manner it will be locatedat a considerable distance from the engine and exhaust manifold. Alsothat when the engine is turned off the induction of hot air from thestove to the coil housing will be discontinued and the rate of coolingof the coil and housing structure will be much greater than the engineand exhaust'manifolds due to the-much greater mass of these latterelements and the remote disposition of the coil with respect thereto.

While the advantage of disposing the temperature' responsive coilelement so as to minimize uncontrolled heatingthereof by the engine isapparent,-it has been found that under the follow-L ing-conditions; aswhen, a'motor vehicle which thereafter diminishes until such differenceceases to give rise to. the aforementioned diificulty.

I It is an object of the present invention to provide an automaticchoking device of the above character, in which the aforementioneddifflculty is overcome by the provision of a secondary temperatureresponsive controllingelement which is;

more directly effectedby the engine temperature.

It is a further object of the present invention. to provide an improvedautomatic choking device having a temperature responsive choke actuatingelement subjected to a controlled temperature during operation of theengine and a secondary temperature responsive element dilimiting thecontrol merit.

rectly effected by the engine temperature for Other objects andadvantages will appear upon reference to the following description andaccompanying drawing. Referring to the drawing:

Fig. l is a side elevation of a downdraft 'carburetor equipped with achoke control mechahas been driven sufficiently to thoroughly-heat theengine and then parked, with the engine turned off, that after a certaininterval econ-- dition exists wherein the temperature responsive coilhas cooled and responded-to move the choke valve to a' position which"willresult in the clearly illustrate.

nism constructed in accordance with the present invention. Parts beingbroken away to more Fig. 2' is a fragmentary section taken on line22ofFig.l.

Fig. 3' is a fragmentary se'ctiontaken on line 3--3 of Fig. 1.

a'rotatable choke shaft 4. The outlet at the lower end of the carburetoris controlled by a throttle valve 5 mounted on a rotatable throttle enda throttle lever I.

The carburetor ismoun-ted on an engine intake manifold 8 and is attachedtheretoby the bolts 9. An engine exhaust manifold isindi- "cated at H)below and parallel to intake mani--.

fold 8. The'near end of the choke shaft 4 cardeliverance of a startingmixturewhich is-too rich for the still comparatively warm engine ifre-started atthis time.

perature within the eng'ine hood enclosure is lowered by drafts of coldair. Obviously, during This difliculty will be aggravated on cold windydays when the .tem-

l of coil l8 engages the projection ii on lever I. Coil I8'isconstructed of a bi-metallic' strip and the cooling down period acritical point is 1 reached at which the difference in'the tempera.

tures of the coil and the engine is greatest and I'i'eS rigidly attachedthereto a'lever in having a bent-up axially extending arm l2 and asecond arm I! which carries pivotally attached thereto alinkl5. Attachedto the air inlet is a therrnostatic. coil housing It having a squaresplit mounting stud i1 rigid y attached thereto which receives andrigidly anchors the inner end of a 1 temperature responsive coil l8; Theouter end so'wound as to tend to unwind with-decreasmg temperatures;Being thus wound and an- "chored at its inner en} theouterend will urgeof the choke actuating ele- I Numeral i indicates a modern downdraftcarburetor having an air inlet 2 at its upper end in l which is mounteda disk-type choke valve ,8 on.

lever II in a counterclockwise or valve closing direction withdecreasing temperatures. A substantial portion of the inside of housingI 6 is lined with insulating material l6a.

Attached to the exhaust manifold I is a stove l9 and a conduit connectsthe stove 19 with the inside of housing IS. A cylinder 2| is formed inthe lower right hand side of housing l6 and has fitted therein a piston22 which is pivotally connected to the link IS. A passageway 23connecting the lower end of cylinder 2| with the carburetor mixingconduit at a point below the throttle valve is provided. A slot 24 inthe wall of the cylinder 2| allows a predetermined amount of by-passingof the piston. The piston 22 responding to suction tends to move thechoke valve open against the resistance of the coil element [8. Thecombination of coil l8 and suction actuated piston 22 provides the wellknown thermo-suction control and its operation is Well understood.

Attached to the choke valve shaft 4 at a point between the housing l6and the air inlet 2 is a lever 25 having a link 25a. pivotally attachedto its outer end at 26. Mounted on a pivot 21 toward the lower end ofthe carburetor is a rotatable throttle blocking element 28 usuallycalled the fast idle cam. The portion of element 28 which extends to theleft of pivot 21 carries a pivot pin 29 which engages the slot 30 in thelower end of link 25a. The portion of element 28 extending to the rightof pivot 21 is provided with an abutting surface 3|. -Attached to thelower flange portion of the carburetor by means of a screw 32 is aU-formed strip of temperature responsive bi-metal 33 positioned so thatat certain temperatures the end of free left leg 34 will block theclockwise rotation of element 28. The

arrangement of the mechanism, as shown, is such that the choke valvewill be held in a substantially open position when element 33 is in aposition to block the clockwise rotation of element 28. Thetemperatureresponsive bi-metallic element 33 is formed with the metalhaving the greater expansion on the inside so that with increasingtemperatures the free leg 34 will move to the left into a blocking,position and to the right out of blocking position (as shown by dottedlines) with decreasing temperatures.

The operation is as follows:

When, after operation, the engine is stopped the flow of warm air fromthe exhaust manifold to the coil housing l6 will stop and the rate ofcooling of the coil 18 will be greater than that of the engine and theblocking element 33 which is positioned closer thereto than coil l8. Asthe coil [8 continues to cool it will uncoil and move the choke valvetoward a closed position. If the rate of cooling of coil l8 has beenappreciably greater than that of element 33, the movement of the chokevalve toward a closed position will be blocked by element 33 as itreaches the position shown. However, as soon as the engine temperaturehas dropped sufficiently for the adjacent element 33 to re-act and moveout of blocking position the choke valve will again be under fullcontrol of element l8. It will be understood that the invention issusceptible to modification, and therefore I do not wish to be limitedin my protection except as set forth in the accompanying claims.

I claim:

1. In an internal combustion engine, a carburetor having a choke valve,a temperature responsive element constructed and arranged to graduallymove said choke valve toward a closed position with decreasingtemperatures, and a second temperature responsive element constructedand arranged to prevent the closing of said choke valve until thetemperature has fallen below a predetermined point, said first mentionedelement being positioned at a greater distance from said engine thansaid last mentioned element.

2. ,In an internal combustion engine having an exhaust manifold, acarburetor having a choke valve, a temperature responsive element forcontrolling said choke valve, and a second temperature responsiveelement constructed and arranged to prevent the closing of said chokevalve until the temperature has fallen below a predetermined point, saidfirst mentioned element being positioned at a greater distance from theengine manifold than said last mentioned element.

3. In a carburetor, a choke valve, a temperature responsive elementconstructed and arranged to gradually close said choke valve withdecreasing temperatures, a second temperature responsive elementconstructed and arranged to block the closing of said choke valve untilthe temperature has fallen below a predetermined point, said lastmentioned element being subjected, under certain conditions, to highertemperature than said first mentioned element.

4. In an internal combustion engine, a carburetor having a choke valve,a temperature responsive element for controlling said choke valve, aninsulated housing for said choke valve, means dependent upon theoperation of the engine for supplying heated air to said housing, and asecond temperature responsive element constructed and arranged to blockthe closing of said choke valve until the temperature has fallen below apredetermined point, said last mentioned element being positioned so asto receive heat from the engine by conduction and radiation moredirectly than said first mentioned element.

5. In an internal combustion engine having a downdraft carburetormounted above the engine, an air inlet to said carburetor at the upperend thereof and a flanged outlet portion at the lower end thereofattached to saidengine, a choke valve in said air inlet, a temperatureresponsive element for controlling said choke valve positioned adjacentsaid choke valve, and mechanism including a second temperature elementfor blocking the closing movement of said choke valve under certainconditions, said second temperature responsive element being positionedadjacent said lower flanged outlet portion.

6. In an internal combustion engine having intake and exhaust manifolds,a downdraft car buretor mounted above said manifold, said carburetorhaving an air inlet at its upper end and a flanged outlet portion at itslower end adjacent said manifold, a choke valve in said air intake, atemperature responsive element for controlling said choke valvepositioned adjacent said air inlet, an insulated housing for said chokevalve, means including intake manifold suction whereby air heated by theexhaust manifold is induced to flow through said housing, and mechanismincluding a second temperature responsive element for limiting thecontrol of said first mentioned temperature responsive element, saidsecond element being positioned adjacent said lower flanged portion.

LELAND B. READ.

